The present invention generally relates to a circulating type of automatic document feeding apparatus and an automatic duplex copying apparatus provided with the apparatus. More particularly, when many copies are made from a plurality of documents arranged in the sequential order of the pages, copy sheets with images being formed in the page order are discharged and also a copying method of fourth types, i.e., duplex copying from a duplex document onto a copy sheet, simplex copying from a duplex document onto a copy sheet, duplex copying from a simplex document, and simplex copying from a simplex document may be effected by easier switching operations. Particularly, an inverting route, wherein after one face of the document has been exposed, the document is inverted so that the other face thereof may be exposed, is provided in the circulating type of automatic document feeding apparatus so that the duplex document may be copied in a short time.
Conventionally, in the copying machine, various types of automatic document feeding apparatuses proposed require resetting of the discharged documents into the document feeding apparatus again by manual operation when the document once copied is recopied The operation is uncertain when the speed becomes higher The operation becomes complicated when many copies are required to be made from the same document and when the copies are required to be made from both faces of the sheet document. Particularly, it is difficult to make many sheets of copies in page order from documents with a plurality of sheets.
Recently, a copying machine provided with a document feeding apparatus which makes it possible to copy a duplex document is proposed in, for example, U.S. Pat. No. 4,099,150 and U.S. Pat. No. 4,140,387, with such various problems as described hereinafter. Namely, in U.S. Pat. No. 4,099,150, an apparatus is proposed which circulates the duplex documents, and inverts the documents via an inverting apparatus during the duplex copying operation. When a document jam has occurred in the apparatus, it is difficult to provide the copied sheets in accordance with the order of the document pages. Also, in U.S. Pat. No. 4,140,387, an apparatus is provided which feeds the duplex documents onto an exposure stand from a document feeding portion and copies them, thereafter reverses them without returning them to the document feeding portion to make outside copies. However, in the apparatus, sheets having unfixed images thereon have to be carried through and inverted by air on the side of the main body of the copying machine in the apparatus, thus resulting in an apparatus higher in price and larger in size. As the apparatus includes a step of inverting the document which has been exposed, a waiting time is required before the exposure completion of the duplex copying step of the former document to present the following document, so that the document exchange time becomes longer, with faster copying speed becoming difficult to obtain.